The current clamp is used to measure the electron current in one wire at a time, the preferred method, but it can also be used to measure more than one wire at a time provided the direction of electron current in each wire is known.

Now that we have a general understanding of electron current through a vehicle ground circuit, we continue begin measuring electron current and understand what each reading is telling us about vehicle electrical circuits during Key ON (KON) and engine run (RUN).

The dual ground configuration is very common but now that batteries are mounted in out-of-the-way places outside of the engine department a single battery ground cable is used to ground the battery negative terminal to the engine block.